The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 840 |
| 2 | 55860 |
| 3 | 1089270 |
| 4 | 3666432 |
| 5 | 5322240 |
| 6 | 8714160 |
| 7 | 10281600 |
| 8 | 20109600 |
| 9 | 21785400 |
| 10 | 32104800 |
| 11 | 9904204800 |
| 12 | 10334134272 |
| 13 | 4660073935104 |
| 14 | 7322605472000 |
| 15 | 11887123248000 |
| 16 | 15387946358400 |
| 17 | 78599399424000 |
| 18 | 516876560449536 |
| 19 | 750304684523520 |
| 20 | 812193794048000 |
[840,55860,1089270,3666432,5322240,8714160, 10281600,20109600,21785400,32104800,9904204800, 10334134272,4660073935104,7322605472000, 11887123248000,15387946358400,78599399424000, 516876560449536,750304684523520,812193794048000] |